1. Field of the Invention
The present invention relates to a conformal array antenna for use with a radar system.
2. Description of the Prior Art
FIG. 1 illustrates a block diagram of a prior art antenna system. In the figure, the reference numeral 1 designates a conformal array antenna including a structural base body 2 assuming a semi-spherical configuration and a number n of antenna units 3.sub.1 to 3.sub.n arrayed on the structural base body 2. A number n of signal lines 4.sub.1 to 4.sub.n interconnect the antenna units 3.sub.1 to 3.sub.n and a microwave beam forming circuit 5. Each of the antenna units 3.sub.1 to 3.sub.n which constitute the conformal array antenna 1 is an independent unitary antenna device.
Next, the operation of the prior art antenna system will be described. A microwave power is received by the antenna units 3.sub.1 to 3.sub.n arrayed on the semi-spherical structural base body 2 of the conformal array antenna 1, and is transmitted via the signal lines 4.sub.1 to 4.sub.n to the microwave beam forming circuit 5 where the microwave signals are synthesized to form a multiplicity of beams by making use of microwave phase shifters, microwave variable attenuators, microwave switches and microwave couplers.
In the thus constructed conventional antenna system, the antenna beams can be arbitrarily formed over the semisphere. In the case of forming a multiplicity of beams by employing microwave devices such as a phase shifter, an attenuator, a switch, a coupler and a distributor, however, the configuration loss becomes larger and only a limited number of beams can be formed concurrently. Supposing that a beam is oriented in a desired direction when used as a part of the radar system, the shadowed units among the antenna units 3.sub.1 to 3.sub.n when viewing the conformal array antenna 1 from the desired direction cannot be effectively utilized. Especially when a scanning angle approximates to 90.degree. from the zenith, almost half of the elements are not available for use.